The most successful affiliates do both.
My college teacher once explained in detail why companies will create products that are similar to other products in their product line. It may seem obvious, but if it was we would all be doing this in affiliate marketing, but most of us aren't.
Companies who invent and sell a coffee maker will go on to make a smaller version of the coffee maker, a version with more features, a portable coffee maker, then they'll branch off into high tech coffee mugs etc.. In short they do this because they already have their foot in the door with advertisers, merchants, and customers. It allows them to select their niche, take it over and always have a very competitive edge when launching a new product in their product line. Affiliates who take this same approach are usually setting themselves up for consistent revenue over a long period of time.
When you've been in a niche for months you start to learn everything encompassing that niche. You learn what works, what doesn't, landing page conversion tactics, what keywords convert, what images convert, you start meeting advertisers, making deals and eventually you become an expert at your niche which allows you to stay competitive and make money for the long run!
To do everything above you need to actually be running traffic, so at this point in time after running a specific niche for a couple months it's fair to say you probably have at least 1 traffic source you know well. So you either need to scale within that traffic source or go and master a 2nd one.
The affiliate game has a lot of angles to it, but being a master in a niche and traffic source is probably the most important thing you can do, it will allow you to make a lot of money on a fairly long term basis. Yeah you may have a rut for a couple weeks, but you'll be making a much more stable income then an affiliate who jumps from 1 niche/traffic source to another on a daily basis.
Think of all the badass people you know who make money. Do they master 1 trade or are they a jack of all trades?

Just to give you an example, a friend of mine has been in the pay day loan niche for 3 years! He's got everything setup in that niche, knows the niche and everyone in it like the back of his hand and you can bet 100 purple diamonds he's doing very well for himself.
Actually doing what's said above is a different story. We all jump from hot niche to hot niche, and from hot traffic source to hot traffic source so most of us won't become experts in niches or traffic sources. It's hard not to jump when it's a fact affiliates can make millions from a hot niche, but only 1/20 or maybe even 1/50 will actually make more than low x,xxx profit from that hot niche.
So for some this creates fast income every couple months, but it's unstable and it's stressful and it's not the way to run a full time business. Choose something, stick with it, master it then come back here and thank me.
This post really opened my eyes to a perspective I had not considered before. Thanks for the insight.
I'm a fan of mastering traffic sources. There is always a trick or two on each source that will always allow you to get ahead of your competitors. I guess that is the same with sticking to a certain niche. However depending on your niche, mastering a big traffic sources is heck of a lot more scalable.
This thought has been running up on my mind for the past 2 months... until I read this post here, which confirms my direction is correct! I've always been in doubt whether should I jump from niche to niche and traffic source to traffic source... I have to say a BIG THANK (hey you notice I not only say here but also pressed the goddamn button?
)to you Jordan for clearing this up!
STM tends to give me some new insights on affiliate marketing whenever I am lost. I love you guys STM <3
Great thread. The more you work with a given traffic source the more you will find out about those 'insider secrets' and the more prolific you will become at it.
I really like your recent posts that talk more about the 'super affiliate mindset' (another example would be your post on 'The Art of Ad Approval') than just showing profitable campaigns ( case studies are of course always appreciated and awesome but I like this stuff better)
thanks, it's just things you start learning after doing it all for years and seeing what makes an affiliate a longterm affiliate rather then a couple lucky campaigns.
While I agree with this post, I still think it's important to get your feet wet in multiple traffic sources early on, just so you know what is out there to experiment with. There are the days where you're running something and you have a hunch that the offer you're running would work great on xxx platform - without getting your feet wet with these platforms, you'd never know.
The biggest hurdle I've found is that a lot of traffic sources require a initial deposits - but many don't. It's good to get a feel for what's out there so you can scale to other traffic sources when the time is right.
I myself, am guilty of trying too many things at once. It is overwhelming, hard to manage, and well, not the most profitable strategy. But at the same time, it gives me a little bit of account history on multiple traffic sources, gives me a bit of a primer on them, an idea of what may work well and what definitely wouldn't work/get approved etc..
Without that, I would be limited in my creative thinking.
My 2 cents at least 
@andy
Thats a good point, to get your feet wet in multiple realms of the industry, especially traffic sources. It'll give you a better instinct of what will work where, but i guess what i was saying comes after this step. Once you know your stuff a bit, it's usually a good move to stick with something for a while, because once your an expert in 1 area it gives you a big boost over your competition.
Sticking with one traffic source is the best for new affiliates. When I first got into this business I jumped around from one thing to the next, and it didn't get me far by any means. When I finally decided to dedicate myself to a single reputable traffic source, I tinkered with it daily and tried a wide variety of targeting options and verticals. Low and behold after a month I had finally hit my first real winning campaign and from there I spawned several other wining campaigns. Fast forward 8 months it's still my primary traffic source and has built me a mid $xxx,xxx business in which I've nearly generated a million dollars in revenue in my first year of affiliate marketing.
Now I dabble in tons of other different smaller traffic sources and have hit some solid winners here and there, stick to one source, master it then when you got the money to play with branch out and experiment with the many other winning traffic sources out there. I sure am glad I stuck it out and mastered the single traffic source. Hard work pays off! Don't give up.
-MJ
Awesome thread!
The thing I love about mastering 1 traffic source is that, once you're really comfortable with it, you will most likely be able to take that experience to a new traffic source and master it faster. You'll be able to relate to stuff better and it gets a bit easier to master your 2nd, 3rd, etc.
For newbies, sticking to 1 niche and 1 traffic source is the way to go...but whatever you do, make sure you're working on something that's 1) scalable (if you're in for big monies) and 2) long term (if something goes down, you should be able to find alternatives).
agreed with hd2010!
Me too started jumping around... without really seeing something good until the point that I decided to stick with only ONE traffic source, then I saw the winners. I am now going to master ONE niche on this ONE traffic source!
always try to have more than 1 traffic source. I learned a valuable lesson a few years ago when google went on their first major round of banning accounts. I was making a killing and lost all my income overnight without a backup plan. I had to scramble to find alternate means of traffic and it took a while to get back to the same level i was at previously.
traffic sources can come and go, can change guidelines, ban accounts, etc. always have a backup plan, dont be stuck with one source of traffic.
one traffic source = 1 income source
Ay I just saw this today - this is a goodass post!
Relevant to the uncertain times we are seeing right now, with everyone looking for the next hot wagon to jump on!
Completely forgot about this post.
STICK with 1 thing, and you'll get good at it. You can quit, but give it a good hundred hours before you even think of quitting. This advice is true with almost everything in life